From U.S. Pat. No. 5,007,480 it is known drilling mud and oil well cement slurries for different purposes such as well cementing, completion fluids, packer fluids, drilling fluids, isolation fluids and other related fluids containing manganomanganic oxide particles as weight agent. The manganomanganic oxide particles are recovered from gases that evolve during oxygen refining of molten ferro-manganese. The particle size of the manganomanganic oxide particles is generally below 10 microns with an average particle diameter less than 1 micron.
One drawback with the use of the manganomanganic oxide particles of U.S. Pat. No. 5,007,480 is the poor flow characteristics of the dry particles. Both for offshore and on-shore use of the manganomanganic oxide particles it would be convenient to use silos for handling and storage of the material. However, due to the poor flow characteristics of the material it is difficult to discharge the material from silo-trucks, silos of delivery boats or stationary silos as the fine particles tend to form bridges in silos and handling systems, particularly in presence of moisture.
For the same reasons it is obvious that metering and feeding of the material into drilling mud and oil well cement slurry from a silo of any size by use of screw conveyors or vibrating devices is inaccurate and unreliable or sometimes even impossible.
The manganomanganic oxide particles loose their flowability after handling and may no longer flow freely after being stored in a silo for a short time. It might result in substantial human effort to remove material from a blocked silo unless the silo is specially designed and are fully equipped with special and expensive devices to handle such sticky material. In some instances the material may therefore also be difficult to move over longer distances using pneumatic transport as commonly by the industry.
Material handled in big bags shows similarly lack of flowability and emptying a big bag through a bottom spout might become impossible and the whole bottom of the bag might be cut away to get the material out.
The same problems as described above in connection with manganomanganic oxide also goes for other powdery minerals used as additives in drilling muds and well cement slurries such as ilmenite, barite and hematite.
Fine dry powders like this will have the ability to behave dusty and have a negative impact on the environment during handling in open air. It may lead to a potential health hazardous situations for the workers due to its manganese-rich content or giving a coloration of the surroundings requiring thorough cleaning resulting in disposals.
To overcome these problems it has been a desire to convert the powdery materials to a particulate agglomerated or granulated powder that gives the required for flow charscterisitics of the material as well as reduced dusting.
Agglomeration of the manganomanganic oxide particles and other powdery minerals to form granules can in principle be done by a number of conventional methods such as briquetting and compaction processes as well various ways of making pellets, spray dried granules or fluidised bed dried products and use of inorganic or organic substances as binding aids.
However, in order to successfully use agglomerated powdery mineral particles in well drilling applications, it is necessary to use binders that make it possible to redisperse the agglomerated particles in a water or an oil phase. Redispersion means that the agglomerates upon dispersion in water or oil are broken down into the original particles. Further, any binders used must be compatible with the well drilling composition it shall be used in.
For this reason non of the traditional ways of making granules, including use of traditional binders, such as molasses, starch, sodium silicate, etc., gives a product that is suitable for the needs when used in the well drilling applications.
As the granules need to be perfectly dispersed applying traditional liquid mixing equipment used by the industry, the particular granulated product must not be stronger bound than the singular particle will be released from the group of particles in a granule to give the desired application effect.
Handling of the granules after processing, through bagging units, storage and transport handling, transfer by use of blowers into silos, compaction due to its weight in a silo, activated with fluidisation, feeding screws, etc. may result in a too early disintegration of the granules thereby causing silo blockages or feeding problems if the granules do not have sufficient strength.
On the one hand: the granules must be stable enough to survive all such handling without disintegration. On the other hand: the granules must be able to easily disintegrate under low shear stress in the liquid application suspension and in dry applications.
Well drilling application mixtures whether cement slurries, drilling, completion and packer fluids, contain a set of additives in the various recipes which has to comply with the required technical characteristics and be compatible with the temperatures and pressures at specific depth of the earth depending on drilling target and work situation. Any use of additives to make granules free flowing and dispersable, also has to show compatibility with other additives in the drilling mixtures.
Since well drilling takes place in an open natural environment by humans, any substances used shall also comply with environmental and safety regulations for use of chemical substances in the nature and by workers.
These above-mentioned requirements set strict limitations to binding additives and other chemical substances to be used for the production of the handling-stable, but easy dispersible granules.
The untreated manganomanganic oxide contains 2-4% of magnetite particles, Fe3O4, as impurities with similar specific gravity. Used as ingredient in drilling mud, such contamination might impregnate the formation surface of the drill-hole and give false magnetic reading on geophysical instruments or drill navigation devices because of its influence on the local natural magnetic field. In processing of manganomanganic oxide to form the desired granules, it is therefore also a need to remove or minimise the content of magnetic particles before the granules are formed.
Some sources of manganomanganic oxide may also contain variable amounts of moisture (0.2%-15%), which after storage and partly drying out will give relatively hard lumps, it all causing problems for handling of the material through any dry processing method or wet processing with only stirring.